Method and system for dynamic ACK/NACK repetition for robust downlink MAC PDU transmission in LTE

ABSTRACT

A method and apparatus for dynamic acknowledgement repetition for a downlink medium access control packet data unit transmission ‘MAC PDU’ requiring multiple acknowledgements, the method having the steps of: receiving the downlink MAC PDU requiring multiple acknowledgements; and utilizing a differentiating factor and acknowledgement scheme, sending the multiple acknowledgements.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority from U.S.patent application Ser. No. 14/156,734, filed on Jan. 16, 2014, which isa continuation and claims priority from U.S. patent application Ser. No.13/476,713, filed May 21, 2012, which is a continuation of and claimspriority from U.S. patent application Ser. No. 11/862,679, filed Sep.27, 2007 and issued as U.S. Pat. No. 8,204,010 on Jun. 19, 2012, whichis a non-provisional of and claims priority from U.S. ProvisionalApplication No. 60/944,644, filed Jun. 18, 2007, all of which areincorporated herein by reference.

FIELD OF THE DISCLOSURE

The present disclosure relates to the long-term evolution (LTE)architecture, and in particular to the acknowledgement of medium accesscontrol packet data units (MAC PDUs) in a long-term evolutionarchitecture.

BACKGROUND

In the long term evolution infrastructure, one proposal being studied isthe use of acknowledgement/negative acknowledgement (ACK/NACK)repetition in order to increase the probability of correct hybridautomatic repeat request (HARQ) feedback signal detection for moreimportant MAC PDUs or in an uplink power limited case. These moreimportant MAC PDUs could, for example, include those containing controlinformation in their body or as part of the header. Discontinuousreception values are one example of control information that could besent in a MAC PDU.

One problem with multiple acknowledgements/negative acknowledgements,hereinafter referred as multiple acknowledgements is that if messagesrequiring multiple feedbacks are sent in adjacent time slots, collisionsbetween the acknowledgements may occur and the enhanced Node B could notdecode the acknowledgements properly due to the collision. Avoidingadjacent time slots creates latency.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will be better understood with reference to thedrawings in which:

FIG. 1 is a dataflow diagram showing communications between an enhancednode B (eNB) and two user equipments (UEs);

FIG. 2 is a dataflow diagram showing communications between an eNB andtwo UEs, where multiple channels are used for robust HARQ feedbacksignaling;

FIG. 3 is a dataflow diagram showing communications between an eNB andtwo UEs, where cyclic shifts are utilized to avoid collisions;

FIG. 4 is a dataflow diagram illustrating communications between an eNBand two UEs, where frequency shifting is utilized to avoid collisions;

FIG. 5 is a dataflow diagram between an eNB and two UEs where cyclicshifting is used for robust signaling within the same time slot;

FIG. 6 is a dataflow diagram between an eNB and two UEs where frequencyshifting is used for robust signaling within the same time slot;

FIG. 7 illustrates a dataflow diagram between an eNB and two UEsutilizing a hybrid system in which robust signaling changes dependent onthe network;

FIG. 8 is a flow chart of an exemplary method in accordance with thepresent disclosure from an eNB perspective;

FIG. 9 is a flow chart of an exemplary method in accordance with thepresent disclosure from the UE perspective;

FIG. 10 is a dataflow diagram showing robust signaling utilizing anacknowledgement scheme dependent on the order of the acknowledgementmessage;

FIG. 11 is a block diagram of an exemplary mobile device apt to be usedwith the present disclosure; and

FIG. 12 is a block diagram of the simplified eNB apt to be used with thepresent disclosure.

DETAILED DESCRIPTION

The present disclosure overcomes latency issues and/or minimizesresource utilization by providing for multiple HARQ feedbacks(acknowledgement or negative acknowledgement) using differentiatingfactors. The differentiating factors allow an eNB to distinguish betweenmultiple HARQ feedbacks received from different UEs in the same timeslot.

In a first embodiment, the differentiating factor is the use of multiplephysical downlink control channels (PDCCHs) for the indication ofmessages having robust response requirements. In the case where twoacknowledgements are required for the message, two PDCCHs can beassigned and messages sent in an odd time slot can be sent on a firstPDCCH and messages sent in an even time slot can be sent in a secondPDCCH, thereby avoiding collisions for messages requiring robustfeedback sent in adjacent time slots.

In a further embodiment, the differentiating factor is the use ofdifferent cyclic shifts of a Constant Amplitude Zero Autocorrelation(CAZAC) sequence to distinguish between feedback messages. Thus, in thecase of robust signaling requiring two HARQ feedbacks, feedbacks formessages sent in odd time slots can utilize the first half of thepossible cyclic shifts and feedbacks for messages sent in even timeslots can utilize a second half of the possible cyclic shifts.

In a further alternative embodiment, frequency blocks can be used as thedifferentiating factor. Thus, in the case of robust signaling requiringtwo HARQ feedbacks, feedbacks for messages sent in odd time slots canutilize a first frequency block within a particular channel andfeedbacks for messages sent in even time slots can utilize a secondfrequency block within the particular channel.

In a further embodiment, a hybrid system can be utilized in whichdifferentiating factors can depend on network conditions. Thus, forexample, if the network is under-utilized, two or more dedicatedchannels can be used for robust HARQ signaling and feedback, wherein ifthe network becomes busy, the number of dedicated channels can bereduced based on allocation of cyclic shifts or frequency blocks. Thechange in the differentiating factor could be signaled to the UEs basedon a broadcast channel or a dedicated message to each UE being servicedby the eNB.

In a further embodiment, instead of utilizing the same resource for allHARQ feedbacks for a message, a scheme for progressing through thedifferentiating factor could be used. Thus, for example, all firstfeedbacks for messages requiring robust HARQ feedback can utilize afirst cyclic shift/first frequency block and all second feedbacks canutilize a second cyclic shift/frequency block.

In a further embodiment, various differentiating features can becombined. Thus, a system may utilize both frequency and cyclic shifting,may utilize multiple PDCCHs and cyclic shifting, or may utilize multiplePDCCHs and frequency shifting. In a further embodiment, all threedifferentiating factors could be used together.

The present disclosure therefore provides a method for dynamicacknowledgement repetition for a downlink medium access control packetdata unit transmission ‘MAC PDU’ requiring multiple acknowledgements,the method comprising the steps of: receiving the downlink MAC PDUrequiring multiple acknowledgements; and utilizing a differentiatingfactor and acknowledgement scheme, sending the multipleacknowledgements.

The present disclosure further provides a user equipment adapted fordynamic acknowledgement repetition for a downlink medium access controlpacket data unit transmission ‘MAC PDU’ requiring multipleacknowledgements, the user equipment characterized by: a communicationssubsystem adapted to receive the downlink MAC PDU requiring multipleacknowledgements; and a processor adapted to utilize a differentiatingfactor and acknowledgement scheme to vary the multiple acknowledgementsfor sending utilizing the communications subsystem.

Reference is now made to FIG. 1. FIG. 1 illustrates a dataflow diagrambetween an enhanced node B (eNB) and two user equipments (UEs). The eNBincludes four physical downlink control channels (PDCCHs), labeled asPDCCH1, PDCCH2, PDCCH3 and PDCCH4. Based on the RANI (Radio AccessNetwork 1) working group agreement that for non-persistent scheduling,the ACK/NACK resource is linked to the index of the control channel(i.e. PDCCH) used for scheduling. Based on this, one or more downlinkcontrol channels can be reserved for scheduling of important MAC PDUs,which require repetition of HARQ (hybrid automatic repeat request)feedback, e.g., ACK/NACK feedback, from the UE for higher liability.

In the example of FIG. 1, PDCCH1, PDCCH2 and PDCCH3 can be linked to asingle ACK/NACK resource, whereas PDCCH4 can be linked to a doubleACK/NACK resource.

The assignment of the reserved PDCCHs and the number of repetitions canbe broadcast on a broadcast control channel (BCCH), for example.

Utilizing the above structure, the eNB of FIG. 1 will use PDCCH1, PDCCH2and PDCCH3 to give a scheduling indication to the UE of a normaldownlink MAC PDU which requires standard reliability. The example ofFIG. 1 uses PDCCH4 to give a scheduling indication to the UE of animportant downlink MAC PDU which requires higher reliability. Forexample, a MAC control PDU or a MAC data PDU with a MAC control headerwhich may include DRX control information. The present disclosure is notmeant to be limited to the types of MAC PDUs that require more robustacknowledgement, and this will be appreciated by those skilled in theart. Any MAC PDU determined by the network to require more robustfeedback could be scheduled on PDCCH4.

In the example of FIG. 1, a signal 110 is sent from the eNB on PDCCH1 attime slot 2*n−3 and is received by the UE at time slot 2*n−1. Generallyeach slot or time unit for data transmission in a cell is numbered bythe system and the number is referred to as System Frame Number (SFN)hereafter. In case of LTE, the SFN refers to the number implicitly orexplicitly assigned to a subframe. The UE1 acknowledges message 110 withacknowledgement 112, which is sent back to the eNB.

A signal 115 is set from PDCCH1 at time slot 2*n−2 and is received atthe UE2 at time slot 2*n. Message 115 is acknowledged in message 117,which is sent back from UE2 to the eNB.

A problem occurs when robust signaling requires multipleacknowledgements. For example, if an important MAC PDU is scheduled forUE1 at time slot 2*n+1, as illustrated by message 120, then theacknowledgement will occur with message 122 at time slot 2*n+3 and withmessage 124 at time slot 2*n+4. Similarly, a subsequent important MACPDU is required to be sent to UE2 at time slot 2*n+2, shown as message130. The acknowledgement of message 130 is performed in messages 132 and134 which start at time slot 2*n+4 and 2*n+5 respectively.

As seen in FIG. 1, the feedback signals from the two UEs use the sameuplink resources including the same frequency band, CAZAC sequence, andcyclic shift of the sequence in the time slot 2*n+5. Due to this, theeNB will have trouble distinguishing between the two feedback signals inthat time slot and this will much increase the error probability. Thisis shown by a collision 140.

As will be appreciated by those skilled in the art, the downlink arrowsof FIG. 1 represent a scheduling indication on PDCCH and transmission ofthe scheduled data on downlink shared channel. Hereafter in thisspecification, the expression that a message is sent on PDCCH is used torefer to that the scheduling indication of the message is sent on PDCCHand actual data is sent on the downlink shared channel using resourcesspecified in the scheduling indication. Meanwhile the uplink arrowsrepresent HARQ feedback using uplink resources indicated by thecorresponding PDCCH.

Various solutions to avoid collision 140 are presented. Reference is nowmade to FIG. 2.

In one embodiment, the eNB could schedule important PDUs with adequateintervals to avoid the collision described in FIG. 1. However, thisleads to the underutilization of dedicated downlink control channels andmay introduce latency when control information needs to be sent to theUEs. In order to reduce the latency, multiple downlink control channelscan be reserved for multiple ACK/NACK repetitions.

In the example of FIG. 2, PDCCH3 and PDCCH4 are utilized to indicateimportant MAC PDU transmissions where two ACKs are acquired.

Referring to FIG. 2, eNB sends a message 210 on PDCCH1 to UE1 at timeslot 2*n−3 and this is acknowledged in time slot 2*n with message 212.

Similarly, a message 220 is sent on PDCCH1 to UE2 at time slot 2*n−2 andis acknowledged in time slot 2*n+1 with message 222.

In the example of FIG. 2, both PDCCH3 and PDCCH4 are linked to uplinkresources for two ACK/NACK repetitions by broadcast control information.In this example, a first message 230 is sent from PDCCH3 to UE1. Thismessage is acknowledged with an acknowledgement 232 in time slot 2*n+3and an acknowledgement 234 in time slot 2*n+4.

Similarly, an important MAC PDU is sent from PDCCH4 to UE2, and is shownas message 240. This is acknowledged with acknowledgements 242 and 244which are sent in time slots 2*n+4 and 2*n+5 respectively.

As seen in FIG. 2, at time slot 2*n+5 no collision occurs since oneacknowledgement, namely acknowledgement 234, is sent to the eNB usingthe resources indicated by PDCCH3 while the other acknowledgement,namely acknowledgement 242, is sent to the eNB using the resourcesindicated by PDCCH4.

In the example of FIG. 2, the selection of which physical downlinkcontrol channel to send an important MAC PDU could be determined basedon the time slot in which the message needs to be sent. For example,PDCCH3 could be used in odd system frame numbers (SFNs) and PDCCH4 couldbe used with even SFNs, as illustrated in FIG. 2. As will beappreciated, the embodiment of FIG. 2 addresses the latency issuedescribed above.

In certain situations, the use of two dedicated physical downlinkcontrol channels leads to system underutilization. As will beappreciated by those skilled in the art, with reference to FIG. 2,PDCCH3 can only be utilized every second time slot and similarly, PDCCH4can only be utilized every second time slot. A further embodiment isdescribed with reference to FIG. 3.

For an efficient single dedicated PDCCH operation, radio resources suchas available cyclic shifts of the CAZAC sequence can be divided intomultiple groups. For example, in the case where feedback requires tworepetitions, half of the available cyclic shifts can be preconfigured toan odd system frame number and the rest can be preconfigured to an evensystem frame number, as shown in FIG. 3.

Specifically, as with the examples of FIG. 1 and FIG. 2, a message 310can be sent on PDCCH1 to UE1 and responded to with acknowledgement 312.

Similarly, a message 320 can be sent on PDCCH1 to UE2 and responded towith an acknowledgement 322.

In the example of FIG. 3, only PDCCH4 is used for resources that requiretwo or multiple ACK or NACK repetitions. In the case of a message 330sent at system frame number 2*n+1, the acknowledgement is sent attimeframe 2*n+3 as acknowledgement 332. Similarly, the secondacknowledgement 334 is sent at timeframe 2*n+4.

Since message 330 originated at a system frame number that is odd, allacknowledgements for that message could utilize a cyclic shift from thefirst group, for example.

Similarly, message 340 is sent from PDCCH4 to UE2 and requires twoacknowledgements. These are sent as acknowledgements 342 and 344.

Since message 340 originated at an even system frame number, a cyclicshift from the second group can be applied to all acknowledgments frommessage 340. In this case, at timeframe 2*n+5 two acknowledgements arereceived by the eNB. However, acknowledgement 334 utilizes a firstcyclic shift and acknowledgement 342 utilizes a second cyclic shift. Inthis way, the eNB is able to distinguish between the HARQ feedbackresources and no collision occurs.

As will be appreciated by those skilled in the art, since the frequencyof important MAC PDUs is much less than the frequency of the remainingtraffic, partitioning uplink HARQ feedback resources, for example, forcyclic shifts, into multiple groups likely will cause no problems withinthe network.

As an alternative to partitioning cyclic shifts, a group of frequencyblocks can be assigned to a dedicated PDCCH and the UE uses frequencyblocks determined by the system frame number when it transmits multipleHARQ feedback. In the case of two repetitions the UE can send the HARQfeedback in one of two frequency blocks in order to avoid collisions.Reference is now made to FIG. 4.

As with FIGS. 1, 2 and 3, a message 410 is sent from PDCCH1 to UE1 andis acknowledged with acknowledgement 412. Similarly, a message 420 issent from PDCCH1 to UE2 and is acknowledged with acknowledgement 422.

An important MAC PDU is received at the eNB and is required to be sentto UE1. This MAC PDU is sent in message 430 and is acknowledged withmessages 432 and 434. Similarly, in the subsequent time slot, animportant message is required to be sent to UE2 and this is sent asmessage 440 and is acknowledged as messages 442 and 444.

Since message 430 originates in time slot 2*n+1, which is an odd systemframe number, acknowledgements for message 430 can utilize a firstfrequency block linked to PDCCH4. Similarly, since message 440originates in time slot 2*n+2, which is an even system frame number,acknowledgements for message 440 can be sent in a second frequency blocklinked to PDCCH4. This is illustrated by acknowledgements 432 and 434proceeding to an area near the top of PDCCH4 in FIG. 4, andacknowledgements 442 and 444 are proceeding to an area near the bottomof PDCCH4 in FIG. 4.

As will be appreciated by those skilled in the art, time slot 2*n+5receives two HARQ feedback responses. These are acknowledgements 434 and442. However, because message 434 uses a first frequency block andacknowledgement 442 uses a second frequency block, the eNB is able todistinguish between the two HARQ feedbacks and thus no collision occurs.

Reference is now made to FIG. 5. FIG. 5 shows an alternative in whichtwo HARQ feedbacks can be sent for a message received within the sametime slot. However, these feedbacks will utilize a different cyclicshift in order to be able to be distinguished by the eNB. Specifically,as with FIGS. 1 to 4, message 510 is sent on PDCCH1 to UE1 and isacknowledged with message 512.

Similarly, message 520 is sent on PDCCH1 to UE2 and is acknowledged withmessage 522.

An important MAC PDU needs to be sent to UE1 and is sent as message 530in time slot 2*n+1. In the example of FIG. 5, two acknowledgements aresent within the subsequent acknowledgement time slot of 2*n+3. These aremessages 532 and 534.

As will be seen from FIG. 5, messages 532 and 534 are both sent withinthe same time slot but utilizing a different cyclic shift and can thusbe distinguished at the eNB.

In the subsequent time slot an important MAC PDU is required to be sent.The important MAC PDU is sent as message 540 on PDCCH4 and isacknowledged with feedbacks 542 and 544 (feedback repetition). Again,messages 542 and 544 are acknowledged within the same time slot andutilize a cyclic shift to enable the eNB to distinguish between the twoacknowledgements. The eNB will simply combine both the acknowledgmentsto improve the reliability.

As will be appreciated by those skilled in the art, referring to FIG. 5,no collisions will occur between subsequent time slots when multipleacknowledgements are required, since all of the multipleacknowledgements are sent within the same time slot utilizing differentcyclic shifts.

Reference is now made to FIG. 6. FIG. 6 shows a data flow diagram inwhich multiple acknowledgements for an important MAC PDU are sent in thesame time slot and differentiated by frequency block. Specifically, amessage 610 is sent from PDCCH1 to UE1. The UE1 acknowledges the messagein acknowledgement 612.

Similarly, a message 620 is sent from PDCCH1 to UE2 and is acknowledgedas message 622.

A downlink MAC PDU requiring multiple HARQ feedback arrives at the eNBin time slot 2*n+1 and is sent to UE1 in message 630. UE1 acknowledgesthe message in time slot 2*n+3 utilizing two acknowledgement messages,namely 632 and 634, within this time slot. Acknowledgements 632 and 634can be distinguished at the eNB based on the different frequency blocksbetween the two acknowledgement messages. The eNB will simply combineboth the acknowledgments to improve the reliability.

Similarly, a message requiring multiple HARQ feedbacks for UE2 arrivesat the eNB and is sent to UE2 in time slot 2*n+2 as shown by message640. Message 640 is acknowledged with acknowledgements 642 and 644,which are again sent within the same time slot and differentiated at theeNB by the different frequency blocks between acknowledgements.

As will be appreciated by those skilled in the art, combinations of theabove could be utilized depending on network conditions. For example,reference is made to FIG. 7. FIG. 7 illustrates a data flow diagram inwhich messages requiring multiple acknowledgements utilize variousschemes for differentiation dependent on network conditions or otherfactors.

In FIG. 7, a message for UE1 arrives which requires multipleacknowledgements. Under the initial differentiation scheme of FIG. 7,the message 710 is sent on PDCCH3 to UE 1 and acknowledgements 712 and714 are sent back from UEI to the eNB. A further message requiringmultiple feedbacks arrives at the eNB for UE2 and is sent in thesubsequent time slot to UE2 from PDCCH4 as message 720. Message 720 isacknowledged with messages 722 and 724. As is seen in time slot 2*n+1multiple acknowledgements are being sent back to the eNB within the sametime slot but because UE 1 utilizes resources indicated by PDCCH3 andUE2 utilizes resources indicated by PDCCH4, no collision occurs.

Subsequent to acknowledgement 722 being sent from UE2, the eNBdetermines that network traffic has increased and the use of dedicatedPDCCHs for multiple acknowledgements should be reduced. In this regard,the eNB may send a message on a broadcast channel that acknowledgementsshould be performed based on a differentiation factor such as a cyclicshift or a frequency block. In the example of FIG. 7, a frequency blockis utilized.

A further message 730 is received by the eNB and is sent on PDCCH4 toUE1 in time slot 2*n+11. A message 740 is received by the eNB and issent on PDCCH4 to UE2 in time slot 2*n+12. Both messages 730 and 740require multiple HARQ feedbacks.

Acknowledgement 732 is sent from UE1 to the eNB in time slot 2*n+13utilizing a first frequency block based on the message broadcast fromthe eNB in the broadcast channel. Similarly, acknowledgement 734 is sentfrom UE1 to the eNB in time slot 2*n+14 utilizing the same frequency asacknowledgement 732.

Acknowledgement 742 is sent from UE2 to the eNB in time slot 2*n+14utilizing a second frequency block based on the message sent from theeNB in the broadcast channel. Similarly, acknowledgement 744 is sentfrom UE2 to the eNB in time slot 2*n+15 utilizing the second frequencyblock.

Since acknowledgements 734 and 742 are both received within time slot2*n+15, a collision would occur without a differentiating factor betweenthe acknowledgements. However, in this case, acknowledgement 734 is senton the first frequency block and acknowledgement 742 is sent on thesecond frequency block, thus allowing the eNB to distinguish between theacknowledgements.

Differentiating factors, as used herein, refer to techniques that allowthe eNB to distinguish between acknowledgement messages received at thesame time slot. These include, but are not limited to, using differentphysical downlink control channels for sending messages that requiremultiple acknowledgements, specifying different cyclic shifts orspecifying different frequency blocks.

In one embodiment, the differentiating factor is utilized based on thetime slot that the initial message is sent in. For example, in the casewhere two acknowledgements are required, messages sent in odd time slotscould be responded to the eNB, utilizing a first cyclic shift orutilizing a first frequency block. Messages sent in even time slotscould be responded to the eNB, utilizing a second cyclic shift orutilizing a second frequency block.

In a further embodiment, the differentiating factor used in the responsecould be based on the acknowledgement number. Specifically, in the aboveit was described that a message sent in an even time slot requiring twoacknowledgements would have both acknowledgements sent utilizing thesecond variation of the differentiating factor, such as the secondcyclic shift. In the further embodiment, this could be replaced byhaving the response to any message require the first acknowledgement toutilize a first variation of the differentiating factor and the secondacknowledgement to utilize a variation of the second differentiatingfactor. For example, all first acknowledgements utilize a firstfrequency block and all second acknowledgements utilize a secondfrequency block.

As will be seen by those skilled in the art, the above will still avoidcollisions within the same time slot for acknowledgements. Specifically,referring to FIG. 10, in the case where the differentiating factor is afrequency block, a message 1010, which requires two acknowledgements issent in time slot 2*n−3. A first acknowledgement 1012 is sent in timeslot 2*n−1 and utilizes a first frequency block. A secondacknowledgement 1014 in response to message 1010 is sent in time slot2*n and utilizes a second frequency block.

Message 1020, which requires multiple acknowledgements, is sent onPDCCH4 to UE2 in time slot 2*n−2 and is acknowledged by acknowledgement1022 in time slot 2*n utilizing a first frequency block and byacknowledgement 1024 in time slot 2*n+1 utilizing a second frequencyblock.

As can be seen from the above time slot 2*n has two acknowledgementssent to the eNB. However, acknowledgement 1014 utilizes the secondfrequency block and acknowledgement 1022 utilizes the first frequencyblock.

Thus, instead of requiring all acknowledgements for a message to utilizethe same variation in the differentiating factor, acknowledgements to amessage must utilize the same progression in the variations indifferentiating factor to avoid collisions.

Reference is now made to FIG. 8. FIG. 8 illustrates a method from theeNB perspective for setting the differentiating factor. Specifically,the process starts at step 810 and proceeds to step 812 in which thedifferentiating factor is broadcast to the UEs. As will be appreciatedby those skilled in the art, the broadcast may occur over any broadcastchannel or may be a dedicated message to UEs being serviced by the eNB.The process then ends at step 814.

Reference is now made to FIG. 9. FIG. 9 illustrates a flow diagram for amethod from a UE perspective. The process starts at step 910 andproceeds to step 912 in which the UE obtains an indication of thedifferentiating factor that it should use. Step 912 could include thedifferentiating factor that is broadcast on a broadcast channel, adedicated message sent to the UE or a preconfigured differentiatingfactor that is either built-in to the UE or provisioned to the UE. Inthe latter cases, changing the differentiating factor is difficult.

The process then proceeds to step 914 in which the UE receives a messagethat requires multiple acknowledgements. Such a message includes, but isnot limited to, a MAC control PDU or a MAC data PDU having controlinformation in its header.

The process then proceeds to step 916 in which acknowledgements are sentto the eNB utilizing the differentiating factor in accordance with apredefined scheme. For example, differentiating factors includedifferent cyclic shifts, or different frequency blocks which areindicated by PDCCHs. The scheme to utilize these differentiating factorscould include a time based scheme where all acknowledgements for amessage sent in a particular time slot utilize the same differentiatingfactor. For example, all acknowledgements to messages sent in odd timeslots could use a first frequency block.

Alternatively, the scheme could include the use of a differentiatingfactor based on the sequence of acknowledgements. For example, everyfirst acknowledgement could utilize the first frequency block and everysecond acknowledgement could utilize the second frequency block.

The process then proceeds to step 918 and ends.

As will be appreciated by those skilled in the art, the method of FIG. 9avoids collisions by allowing the eNB to distinguish or differentiatebetween acknowledgements received in the same time slot. Further latencyissues are reduced, and in the case of cyclic or frequency shifting,network resources are more fully utilized.

The above examples use the requirement of two acknowledgements forcertain MAC PDUs. However, the above techniques can be expanded formessages requiring more than two acknowledgements. In this case, thenumber of dedicated physical downlink control channels could equal thenumber of acknowledgements required, the number of cyclic shift groupscould equal the number of acknowledgements required or the number offrequency blocks could equal the number of acknowledgements required.

In a further expansion to the above, various differentiating factorscould be utilized together in order to increase the number ofdistinguishing features for acknowledgements while not placing undueburdens on the network. Specifically, a network may be limited to thenumber of dedicated physical downlink control channels that can beutilized for multiple acknowledgement messages, the number of cyclicshifts that can be distinguished, or the number of frequency shifts thatcan be distinguished.

Thus, a system requiring more than two acknowledgements could combinefrequency blocks and cyclic shifts, physical downlink control channeland frequency blocks, or physical downlink control channel and cyclicshifts. An example in which four acknowledgements are required couldutilize a first cyclic shift and first frequency shift in a first timeslot, the first cyclic shift and second frequency shift in a second timeslot, the second cyclic shift and a first frequency shift in a thirdtime slot and the second cyclic shift and second frequency shift in thefourth time slot. Various alternatives to the above would be evident tothose skilled in the art having regard to the present disclosure. Thepresent disclosure is not meant to limit the combination ofdifferentiating factors to any specific grouping.

The above can be implemented on any UE and eNB. An exemplary UE isdescribed with reference to FIG. 11. The present disclosure is not meantto be limited to the embodiment of FIG. 11, however, and any UE can beutilized.

FIG. 11 is a block diagram illustrating user equipment apt to be usedwith preferred embodiments of the apparatus and method of the presentapplication. User equipment 1100 is preferably a two-way wirelesscommunication device having at least voice and data communicationcapabilities. User equipment 1100 preferably has the capability tocommunicate with other computer systems on the Internet.

User equipment 1100 incorporates a communication subsystem 1111,including both a receiver 1112 and a transmitter 1114, as well asassociated components such as one or more, preferably embedded orinternal, antenna elements 1116 and 1118, local oscillators (LOs) 1113,and a processing module such as a digital signal processor (DSP) 1120.As will be apparent to those skilled in the field of communications, theparticular design of the communication subsystem 1111 will be dependentupon the communication network in which the device is intended tooperate.

An LTE user equipment may require a removable user identity module(RUIM) or a subscriber identity module (SIM) card in order to operate ona network. The SIM/RUIM interface 1144 is normally similar to acard-slot into which a SIM/RUIM card can be inserted and ejected like adiskette or PCMCIA card. The SIM/RUIM card can have approximately 64 Kof memory and hold many key configurations 1151, and other information1153 such as identification, and subscriber related information.

When required network registration or activation procedures have beencompleted, user equipment 1100 may send and receive communicationsignals over a network 1119. As illustrated in FIG. 11, network 1119 canconsist of multiple base stations communicating with the user equipment.

Signals received by antenna 1116 through communication network 1119 areinput to receiver 1112, which may perform such common receiver functionsas signal amplification, frequency down conversion, filtering, channelselection and the like, and in the example system shown in FIG. 11,analog to digital (ND) conversion. A/D conversion of a received signalallows more complex communication functions such as demodulation anddecoding to be performed in the DSP 1120. In a similar manner, signalsto be transmitted are processed, including modulation and encoding forexample, by DSP 1120 and input to transmitter 1114 for digital to analogconversion, frequency up conversion, filtering, amplification andtransmission over the communication network 1119 via antenna 1118. DSP1120 not only processes communication signals, but also provides forreceiver and transmitter control. For example, the gains applied tocommunication signals in receiver 1112 and transmitter 1114 may beadaptively controlled through automatic gain control algorithmsimplemented in DSP 1120.

User equipment 1100 preferably includes a microprocessor 1138 whichcontrols the overall operation of the device. Communication functions,including at least data and voice communications, are performed throughcommunication subsystem 1111. Microprocessor 1138 also interacts withfurther device subsystems such as the display 1122, flash memory 1124,random access memory (RAM) 1126, auxiliary input/output (I/O) subsystems1128, serial port 1130, one or more keyboards or keypads 1132, speaker1134, microphone 1136, other communication subsystem 1140 such as ashort-range communications subsystem and any other device subsystemsgenerally designated as 1142. Serial port 1130 could include a USB portor other port known to those in the art.

Some of the subsystems shown in FIG. 11 perform communication-relatedfunctions, whereas other subsystems may provide “resident” or on-devicefunctions. Notably, some subsystems, such as keyboard 1132 and display1122, for example, may be used for both communication-related functions,such as entering a text message for transmission over a communicationnetwork, and device-resident functions such as a calculator or tasklist.

Operating system software used by the microprocessor 1138 is preferablystored in a persistent store such as flash memory 1124, which mayinstead be a read-only memory (ROM) or similar storage element (notshown). Those skilled in the art will appreciate that the operatingsystem, specific device applications, or parts thereof, may betemporarily loaded into a volatile memory such as RAM 1126. Receivedcommunication signals may also be stored in RAM 1126.

As shown, flash memory 1124 can be segregated into different areas forboth computer programs 1158 and program data storage 1150, 1152, 1154and 1156. These different storage types indicate that each program canallocate a portion of flash memory 1124 for their own data storagerequirements. Microprocessor 1138, in addition to its operating systemfunctions, preferably enables execution of software applications on theuser equipment. A predetermined set of applications that control basicoperations, including at least data and voice communication applicationsfor example, will normally be installed on user equipment 1100 duringmanufacturing. Other applications could be installed subsequently ordynamically.

A preferred software application may be a personal information manager(PIM) application having the ability to organize and manage data itemsrelating to the user of the user equipment such as, but not limited to,e-mail, calendar events, voice mails, appointments, and task items.Naturally, one or more memory stores would be available on the userequipment to facilitate storage of PIM data items. Such PIM applicationwould preferably have the ability to send and receive data items, viathe wireless network 1119. In a preferred embodiment, the PIM data itemsare seamlessly integrated, synchronized and updated, via the wirelessnetwork 1119, with the user equipment user's corresponding data itemsstored or associated with a host computer system. Further applicationsmay also be loaded onto the user equipment 1100 through the network1119, an auxiliary I/O subsystem 1128, serial port 1130, short-rangecommunications subsystem 1140 or any other suitable subsystem 1142, andinstalled by a user in the RAM 1126 or preferably a non-volatile store(not shown) for execution by the microprocessor 1138. Such flexibilityin application installation increases the functionality of the deviceand may provide enhanced on-device functions, communication-relatedfunctions, or both. For example, secure communication applications mayenable electronic commerce functions and other such financialtransactions to be performed using the user equipment 1100.

In a data communication mode, a received signal such as a text messageor web page download will be processed by the communication subsystem1111 and input to the microprocessor 1138, which preferably furtherprocesses the received signal for output to the display 1122, oralternatively to an auxiliary I/O device 1128.

A user of user equipment 1100 may also compose data items such as emailmessages for example, using the keyboard 1132, which is preferably acomplete alphanumeric keyboard or telephone-type keypad, in conjunctionwith the display 1122 and possibly an auxiliary I/O device 1128. Suchcomposed items may then be transmitted over a communication networkthrough the communication subsystem 1111.

For voice communications, overall operation of user equipment 1100 issimilar, except that received signals would preferably be output to aspeaker 1134 and signals for transmission would be generated by amicrophone 1136. Alternative voice or audio I/O subsystems, such as avoice message recording subsystem, may also be implemented on userequipment 1100. Although voice or audio signal output is preferablyaccomplished primarily through the speaker 1134, display 1122 may alsobe used to provide an indication of the identity of a calling party, theduration of a voice call, or other voice call related information forexample.

Serial port 1130 in FIG. 11 would normally be implemented in a personaldigital assistant (PDA)-type user equipment for which synchronizationwith a user's desktop computer (not shown) may be desirable, but is anoptional device component. Such a port 1130 would enable a user to setpreferences through an external device or software application and wouldextend the capabilities of user equipment 1100 by providing forinformation or software downloads to user equipment 1100 other thanthrough a wireless communication network. The alternate download pathmay for example be used to load an encryption key onto the devicethrough a direct and thus reliable and trusted connection to therebyenable secure device communication. As will be appreciated by thoseskilled in the art, serial port 1130 can further be used to connect themobile device to a computer to act as a modem.

Other communications subsystems 1140, such as a short-rangecommunications subsystem, is a further optional component which mayprovide for communication between user equipment 1100 and differentsystems or devices, which need not necessarily be similar devices. Forexample, the subsystem 1140 may include an infrared device andassociated circuits and components or a Bluetooth™ communication moduleto provide for communication with similarly enabled systems and devices.

Referring to FIG. 12, a simplified enhanced Node B 1210 is provided.Enhanced Node B 1210 includes a communications subsystem 1212 forcommunication with user equipment and further for receiving data from anetwork.

Enhanced Node B further includes a buffer 1214 to store data that is tobe passed to a UE.

Enhanced Node B further includes a processor 1216 adapted to initiatesignaling and process responses in accordance with the embodiment ofFIGS. 1 to 10 herein.

The embodiments described herein are examples of structures, systems ormethods having elements corresponding to elements of the techniques ofthis application. This written description may enable those skilled inthe art to make and use embodiments having alternative elements thatlikewise correspond to the elements of the techniques of thisapplication. The intended scope of the techniques of this applicationthus includes other structures, systems or methods.

The invention claimed is:
 1. A method performed by a user equipment toprovide acknowledgement (ACK) or negative acknowledgement (NACK)feedback regarding a downlink transmission, the method comprising: uponreceipt of the downlink transmission: transmitting, by the userequipment, a first ACK/NACK feedback response corresponding to thedownlink transmission in a first subframe using a first cyclic shift,and transmitting, by the user equipment, a plurality of additionalACK/NACK feedback responses corresponding to the same downlinktransmission, each of the plurality of additional ACK/NACK feedbackresponses corresponding to the same downlink transmission beingtransmitted in a respective subframe using a respective cyclic shiftdifferent from the first cyclic shift used by the first ACK/NACKresponse corresponding to the same downlink transmission.
 2. The methodof claim 1, wherein each of the plurality of additional ACK/NACKfeedback responses is a repetition of the first ACK/NACK feedbackresponse.
 3. The method of claim 1, wherein each of the respectivesubframes is a subframe following the first subframe.
 4. The method ofclaim 1, wherein the first ACK/NACK feedback response is transmittedusing a first uplink transmission resource, and the first uplinktransmission resource is determined based on a location of a physicaldownlink control channel.
 5. The method of claim 1, wherein the firstACK/NACK feedback response is transmitted using a first uplinktransmission resource, and the first uplink transmission resource isdetermined based on an index associated with a physical downlink controlchannel.
 6. The method of claim 1, wherein the downlink transmission isa single transmission of a Medium Access Control (MAC) Protocol DataUnit (PDU).
 7. A user equipment comprising: a receiver configured toreceive a downlink transmission; and a transmitter configured to provideacknowledgement (ACK) or negative acknowledgement (NACK) feedback uponreceipt of the downlink transmission by transmitting a first ACK/NACKfeedback response corresponding to the downlink transmission in a firstsubframe using a first cyclic shift, and transmitting a plurality ofadditional ACK/NACK feedback responses corresponding to the samedownlink transmission, each of the plurality of additional ACK responsescorresponding to the same downlink transmission being transmitted in arespective subframe using a respective cyclic shift different from thefirst cyclic shift used by the first ACK/NACK response corresponding tothe same downlink transmission.
 8. The user equipment of claim 7,wherein each of the plurality of additional ACK/NACK feedback responsesis a repetition of the first ACK/NACK feedback response.
 9. The userequipment of claim 7, wherein the first ACK/NACK feedback response istransmitted using a first uplink transmission resource, and the firstuplink transmission resource is determined based on a location of aphysical downlink control channel.
 10. The user equipment of claim 7,wherein the first ACK/NACK feedback response is transmitted using afirst uplink transmission resource, and the first uplink transmissionresource is determined based on an index associated with a physicaldownlink control channel.
 11. A method performed by a user equipment forproviding acknowledgement (ACK) or a negative acknowledgement (NACK)feedback, the method comprising: transmitting, by a transmitter of theuser equipment, a first ACK/NACK response corresponding to a downlinktransmission, the first ACK/NACK response transmitted in a firstsubframe using a first cyclic shift; and repeating transmission, by thetransmitter of the user equipment, of additional ACK/NACK responsescorresponding to the same downlink transmission, each of the pluralityof additional ACK/NACK responses corresponding to the same downlinktransmission being transmitted in a respective subframe using arespective cyclic shift different from the first cyclic shift used bythe first ACK/NACK response corresponding to the same downlinktransmission.
 12. A user equipment for providing acknowledgement (ACK)or a negative acknowledgement (NACK) feedback, the user equipmentcomprising: a receiver configured to receive a downlink transmission;and a transmitter configured to transmit a first ACK/NACK responsecorresponding to the downlink transmission, the first ACK/NACK responsetransmitted in a first subframe using a first cyclic shift, and repeattransmission of additional ACK/NACK responses corresponding to the samedownlink transmission, each of the plurality of additional ACK/NACKresponses corresponding to the same downlink transmission beingtransmitted in a respective subframe using a respective cyclic shiftdifferent from the first cyclic shift used by the first ACK/NACKresponse corresponding to the same downlink transmission.
 13. A methodperformed by a user equipment to provide acknowledgement (ACK) ornegative acknowledgement (NACK) feedback regarding a downlinktransmission, the method comprising: upon receipt of the downlinktransmission: transmitting, by the user equipment, a first ACK/NACKfeedback response corresponding to the downlink transmission in a firstsubframe using a first cyclic shift; transmitting, by the userequipment, a second ACK/NACK feedback response corresponding to the samedownlink transmission in a second subframe using a second cyclic shiftdifferent from the first cyclic shift; and transmitting, by the userequipment, a third ACK/NACK feedback response corresponding to the samedownlink transmission in a third subframe using the second cyclic shift,wherein the second ACK/NACK feedback response and third ACK/NACKfeedback response are repetitions of the first ACK/NACK response.
 14. Auser equipment, comprising: a receiver configured to receive a downlinktransmission; and a transmitter configured to provide acknowledgement(ACK) or negative acknowledgement (NACK) feedback upon receipt of thedownlink transmission by transmitting a first ACK/NACK feedback responsecorresponding to the downlink transmission in a first subframe using afirst cyclic shift, transmitting a second ACK/NACK feedback responsecorresponding to the same downlink transmission in a second subframeusing a second cyclic shift different from the first cyclic shift, andtransmitting a third ACK/NACK feedback response corresponding to thesame downlink transmission in a third subframe using the second cyclicshift, wherein the second ACK/NACK feedback response and third ACK/NACKfeedback response are repetitions of the first ACK/NACK response.